This invention is related generally to improved plug apparatus and, more specifically, to plug apparatus providing improved resistance to liquid and material flow.
Many types of manufactured parts, such as parts used in the manufacture of automobiles and machinery, must be coated with various materials and substances to adapt those parts for their intended end use. The coatings impart desired characteristics to the parts, such as resistance to corrosion or friction. Many different types of materials can be applied to the parts including nylons, polycarbonates, metals, etc. Among the well-known types of coating operations used to apply various substances to parts include coating by powder coating, anodizing and plating.
In all of these coating operations, the surface portions of the part are completely exposed to the coating substance. In powder coating operations the part to be coated is typically electrostatically charged and heated and then exposed to a fine particulate spray or fluidized bed of oppositely-charged coating particles. The particles are attracted to the surface to be coated and are melted, forming a coating over the part. In anodizing and plating operations, the part to be coated is charged and then dipped into a bath containing the coating material. The coating material is attracted to the part and is deposited onto the exposed surface portions of the part.
Many types of parts to be coated include internal surface portions which must not be coated. These types of parts are typically three-dimensional, include outer and inner surface portions and include various openings (also known as holes) in the part outer surface through which coating materials could enter the part and undesirably come into contact with the internal surface portions of the part.
It may be undesirable to apply a coating to the internal surface portions of these types of parts for many reasons. For example, it may be undesirable to apply a coating to the internal surface portions of a valve or pipe because that coating may be incompatible with fluids or gases to be conveyed through the valve or pipe. Also by way of example, it may be undesirable to apply a coating to threads cut in the internal surface portion of an annular opening in a tube or other part because that coating may interfere with operation of the threads. It may be undesirable for the liquid media used in plating or anodizing operations to come into contact with the internal surface portions of a part because the media can damage the internal surface portions of the part.
Various products have been developed to mask, or close, the openings in these parts thereby preventing coating materials from coming into contact with the internal surface portions of the parts. For example, a variety of caps and plugs are commercially available to mask openings in the part to be coated. These masking devices are configured for the particular application. For example, plugs are intended to be inserted into the opening. The plug has a tapered outer body at least a portion of which has an outside diameter which is larger than the inside diameter of the opening. The plug is held in place by the frictional fit between the plug outer body and the walls forming the opening in the part.
Conventional plugs are available in many sizes and shapes and include configurations ranging from gently tapered annular plug bodies to plug bodies having pronounced conical designs. Conventional plugs are available in many types of materials including, for example, cork, silicone and EPDM rubber.
Conventional plugs are quite suitable for use in masking most openings in parts and for use with most coating operations. However, these types of masking devices may provide a less-than-complete seal under certain circumstances. For example, certain types of parts may include a confined void volume formed by internal walls of the part and the plug inserted into the opening in the part. If the part is to be heated as part of the coating operation, gas inside the part void volume can expand, potentially forcing the plug partially or completely out of the opening. Failure of the plug may undesirably expose the internal surface portions of the part to the coating material.
By way of further example, conventional plugs may form a less-than-complete seal around a threaded opening in the part, particularly where the threads are cut deeply into the walls forming the opening. A less-than-complete seal in such a threaded opening may permit coating materials, such as the liquid media used in plating and anodizing operations, to enter into the interior surface portions of the part by flowing along the threads.
Other types of commercially-available plugs for masking openings in parts include apparatus to more completely engage the plug body with the opening walls. These conventional devices include a plug body made of a compressible material and a lever arm with a camming apparatus or other compressing apparatus. The compressing apparatus applies force to the plug body thereby compressing the plug body and expanding the plug circumferentially forming a tight fit between the plug and the opening walls.
Compressible plugs are advantageous because they are less likely to be dislodged from an opening by the expanding gas forces within a heated part. In addition, the tight seal formed between the compressible plug and the part can form a more complete seal between the plug body and a threaded opening, particularly where the plug body is made of a soft material which can conform to the threads.
However, conventional compressible plugs may not be suitable for use in all coating applications, particularly those applications in which the part is immersed in a liquid media. It has been found that liquid media (such as used in anodizing and plating operations) can flow through an axial opening provided in the plug body and into interior portions of the part. The axial opening is coextensive with the plug body and is provided so that a rod may be inserted through the plug body to join opposed external plates between which the plug body is compressed.
Passage of even a small amount of liquid media between the external plates, through the plug body and against the interior surface portions of the part can severely damage the part. The damage may be so extensive that the part must be discarded or the part may require repair and remediation at undue cost. As can be understood, damage of parts is a particular problem in large scale coating operations, such as those found in the automotive industry. Loss of, or damage to, even a small percentage of the parts to be coated can result in significant monetary loss to the manufacturer.
It would be significant improvement in the art to provide a plug for masking one or more openings in a part to be coated which would form a complete seal between the plug and opening walls of the part to be coated, which would prevent passage of liquids and other coating materials through the internal plug body, which would be simple and easy to use and which would be reusable.
It is an object of this invention to provide an improved plug apparatus which overcomes problems and shortcomings of the prior art.
Another object of this invention is to provide an improved plug apparatus which completely seals an opening in a part, particularly to prevent liquids and other materials from entering the opening.
A further object of this invention is to provide an improved plug apparatus which completely seals an opening in a part and which prevents passage of liquids and other materials into the part through the internal plug body.
Yet another object is to provide an improved plug apparatus which is simple and easy to use.
Still another object of this invention is to provide an improved plug apparatus which forms a tight seal across an opening in a part.
An additional object is to provide an improved plug apparatus which is reusable.
How these and other objects are accomplished will be apparent from the descriptions of this invention which follow.